Nowadays, scanning apparatuses such as multifunction peripherals or image scanners become essential electronic devices in the office or home. The scanning apparatuses are widely used for scanning images of documents, photographs or films. The scanned images can be converted into electronic files, which are then stored, processed, spread or modified. With increasing development of scanning technologies, the scanners are designed in views of miniaturization, good imaging quality and cost-effectiveness.
Generally, after a scanning apparatus is turned on, a warm-up activity is performed by the scanner. During the warm-up period, a calibrating operation is performed on a calibration plate to acquire standard image data. The standard image data are used as reference basis for correcting and compensating the systematic color level. In other words, the calibrating operation may compensate the color shift of the scanned image and correct the starting position of the scanning range of the scanner.
FIG. 1 is a schematic view illustrating a scanning apparatus with a position-calibrating structure according to the prior art. As shown in FIG. 1, the conventional scanning apparatus 1 has a scanning platform 10. A position-calibrating structure 101 is disposed on the scanning platform 10. A scanning module 102 is disposed under the scanning platform 10. In addition, the scanning platform 10 has a scanning window 103. In a case that the scanning module 102 is located at the starting position of the scanning range, the position-calibrating structure 101 is arranged between the scanning module 102 and the scanning window 103.
The position-calibrating structure 101 comprises a pair of color plates with strong color contrast. For example, the position-calibrating structure 101 comprises a white calibration plate 101a and a black calibration plate 101b. The white calibration plate 101a is disposed on the scanning platform 10. The black calibration plate 101b is arranged beside the scanning window 103, and aligned with and partially overlapped with the white calibration plate 101a. In addition, a light-emitting element (not shown) and an image reader (not shown) are disposed within the scanning module 102. A document 104 to be scanned is placed on the scanning window 103. A light beam emitted from the light-emitting element is projected on the document 104, and the reflected light beam is received by the image reader within the scanning module 102. As a consequence, the image data of the document 104 are obtained and saved as an electronic file.
For performing a position-calibrating operation of the scanning module 102, the scanning module 102 is moved in a scanning direction B. When the scanning module 102 is moved to the position corresponding to the white calibration plate 101a of the position-calibrating structure 101, the light beam emitted from the light-emitting element is reflected by the white calibration plate 101a and then received by the image reader. Meanwhile, a color level correction is performed. Then, the scanning module 102 is continuously moved in a scanning direction B to the position corresponding to the black calibration plate 101b of the position-calibrating structure 101. According to the color contrast between the white calibration plate 101a and the black calibration plate 101b when the scanning module 102 is moved from the white calibration plate 101a to the black calibration plate 101b, a sensing voltage difference is detected to judge the starting position of the scanning range of the scanning module.
The use of the position-calibrating structure 101, however, still has some drawbacks. For example, when the scanning module 102 is moved to the junction between the white calibration plate 101a and the black calibration plate 101b, the sensing voltage is unstable and the transition region fluctuates (see the circled zone 22 as shown in FIG. 2). In this situation, the data for color level calibration are insufficient (see the circled zone 21 as shown in FIG. 2). The image reader within the scanning module 102 may be suffered from erroneous judgment, so that the accuracy of the color level calibration is usually unsatisfied. Moreover, if the document 104 is similar to the position-calibrating structure 101, the scanning module 102 may erroneously judge the starting position of the scanning range. In this situation, the accuracy of the color level calibration and the accuracy of positioning the starting position of the scanning range will be impaired and thus the imaging quality of the scanned image will be deteriorated.
FIG. 3 is a schematic view illustrating another scanning apparatus with a position-calibrating structure according to the prior art. As shown in FIG. 3, the position-calibrating structure 101 comprises a white calibration plate 101a and a home sensor 101c. For performing a position-calibrating operation of the scanning module 102, the scanning module 102 is moved in a scanning direction B. When the scanning module 102 is moved to the position corresponding to the home sensor 101c, the home sensor 101c issues a notifying signal to prompt the starting position of the scanning module 102.
Although the uses of the white calibration plate 101a and the home sensor 101c are effective for correcting the starting position and the color level, the home sensor 101c increases the fabricating cost of the scanning apparatus 1.
For obviating the drawbacks encountered from the prior art, there is a need of providing a calibrating and positioning structure of a scanning apparatus.